[Libreoffice] From sal/cppunit.h to sal/precppunit.hxx

Hi all,

With 
<http://cgit.freedesktop.org/libreoffice/core/commit/?id=d996328cd5f46eeed2df0cbd510eda28e2f7cef9> 
come three changes for CppUnit based tests in the LibO code base:

- The header sal/cppunit.h has been removed (and it was not used much).

- There is a new header sal/precppunit.hxx that should be included in 
every file (.hxx or .cxx) that includes any cppunit/... headers.  What 
it does at the moment is override CPPUNIT_PLUGIN_EXPORT (see next), but 
it might get extended in the future.  This means that the first headers 
included into any file (.hxx or .cxx) should now follow the pattern

  [#include "precompiled_XXX.hxx"]
   #include "sal/config.h"
  [#include "sal/precppunit.hxx"]

- The overridden CPPUNIT_PLUGIN_EXPORT exports the cppunitTestPlugIn 
function via symbol visibility, so there is no longer a need to export 
it via a map file.  (For dmake-based code, that means use 
VISIBILITY_HIDDEN=TRUE and SHLnUSE_EXPORTS=name instead of 
SHLnVERSIONMAP=...  This feature was also already available with the old 
sal/cppunit.h, but lots of places in the code still used map files.  I 
changed this to exclusively use symbol visibility now.)

-Stephan